Support passing multipe orgs when using deep sync

[se7entyse7en]

Currently, shallow sync supports passing multiple orgs, but deep sync doesn't.

[alexpdp7]

Maxim said somewhere else...

Maybe it's easier to contribute to ghsync repo?

You just need to copy-past code from here: https://github.com/src-d/ghsync/blob/master/cmd/ghsync/subcmd/shallow.go#L44 to here: https://github.com/src-d/ghsync/blob/master/cmd/ghsync/subcmd/deep.go#L55